Hall Electrolytic Conductivity Detector Research Articles

Determination of organochlorine and organophosphorus pesticide residues in low moisture, nonfatty products using a solid phase extraction cleanup and gas chromatography

A multiresidue solid‐phase extraction (SPE) method for the isolation and subsequent gas Chromatographie determination of organochlorine and organophosphorus pesticide residues in low‐moisture, nonfatty products is described. Residues are extracted from samples with an acetonitrile/water mixture. Cleanup of the extract is performed using graphitized carbon black and anion exchange SPE columns, and analysis is performed by gas chromatography with Hall electrolytic conductivity and flame photometric detection. Recovery data was obtained by fortifying corn, oats and wheat with pesticides. The average recoveries were 79–123% for eight organochlorine and 51–122% for 28 organophosphorus pesticide residues. The limit of quantitation for chlorpyriphos was 0.05 ppm using the Hall electrolytic conductivity detector and <0.005 ppm using the flame photometric detector.

GC determination of halogenated olefins by photoionization and hall electrolytic conductivity detectors in series in matrices of hydrofluorocarbons and hydrochlorofluorocarbons

Gas chromatography (GC) with photoionization (PI) and Hall electrolytic conductivity (E1C) detectors connected in series, has been used for the determination of chlorofluorinated olefins. The separation of different standard solutions containing eight chlorofluorinated ethenes in nitrogen and in halogenated matrices has been performed in wide bore capillaries, 0.53 mm i.d., and normal capillaries, 0.32 mm i.d. The quality of separation is obviously influenced by their limited load capacity and by the response time of the Hall detector. At concentrations 1–150 μL L−1 halogenated olefins, both PI and ElC detectors have linear response and can detect minimum levels of 0.2–0.5 ng and 0.4–1.2 ng, respectively. The PID is particularly selective toward halogenated olefins and is extremely useful for the determination of traces of unsaturated halogenated hydrocarbons in a matrix of saturated homologues. The results of this work are of great interest for the detection of chorofluorinated olefins, highly toxic compounds usually formed as by-products in the industrial production of hydrofluorocarbons and hydrochloro-flurocarbons.

Comprehensive, quantitative, congener-specific analyses of eight aroclors and complete PCB congener assignments on DB-1 capillary GC columns

We have determined complete polychlorinated biphenyl (PCB) congener assignments and weight percent distributions for all major (> 0.5 wt %) PCB components of Aroclors 1221, 1232, 1242, 1016, 1248, 1254, 1260, 1262 that are resolved by DB-1 (polydimethylsiloxane) capillary GC columns. Aroclor components present between 0.05 and 0.5 wt % were also identified but not quantified. Quantitation was done using a combination of GC-ELCD (Hall electrolytic conductivity detector) and GC-MS measurements. All 209 PCB congeners have been assigned to the 124 peaks that can be resolved on DB-1 columns. The data support use of these eight Aroclors individually or in customized standards for calibrating the comprehensive, quantitative, congener-specific PCB analyses that are necessary for accurate quantitation of the complex and often radically altered mixtures of PCBs typically found in the environment.

Methyl Bromide Determination in Selected Foods by Headspace Technique

A headspace method used earlier for determining methyl bromide (MB) in assorted nuts and peanut butters has been successfully applied to other foods that could potentially contain traces of this toxic fumigant. The foods tested include 63 off-the-shelf spices and seasonings, 83 table-ready items (grain-based, dried, or highly seasoned), 30 dried fruits and trail mixes, and 38 oil-based items (oil-seeds, cooking oils, or spicy oil-based dressings). Sample headspace gas is produced by blending < or = 50 g sample in 250 +/- 50 mL aqueous solution in a sealed 1000 mL blender cup. After equilibration at 25 degrees C, the headspace is sampled with a gas-tight syringe and injected into a dual column-dual detector gas chromatograph. One determination is made with a 20% OV-101 packed column and a 63Ni electron capture detector (ECD), the other with a GS-Q wide-bore capillary column and a Hall electrolytic conductivity detector (HECD). Of the approximately 200 samples tested, none contained detectable MB residue at a quantitation limit < 100 ng/g sample. All fortified samples yielded MB recovery. Samples were fortified at levels ranging from 78 to 3250 ng MB/g. Recoveries ranged from a mean high of 56% for spices and seasonings to a mean low of 30% for oil-based foods. The overall recovery and CV, including the results from assorted nuts and peanut butters, were 46 and 33%, respectively.

Capillary gas chromatographic method for the determination of the thromboxane A 2 receptor antagonist S-1452 and its metabolites in human urine

A capillary gas chromatographic method using a sulphur-specific detector (Hall's electrolytic conductivity detector) was established to determine the thromboxane A 2 antagonist S-1452 and its metabolites in human urine. The target species were the free acid (+)-S-145 of the drug and its nine metabolites: the three hydroxyl forms of (+)-S-145 (I, II and III), bisnor-(+)-S-145 (IV) the hydroxylated forms of IV (V and VI), tetranor-(+)-S-145 (VII) and the hydroxylated forms of VII (VIII and IX). These ten compounds, which have the same sulphur-containing functional group in common, were determined simultaneously. Their conjugated forms, which were assumed to be glucuronides, were also assayed after hydrolysis. The first derivatization was esterification with diazomethane. The second, for the hydroxylated compounds, was trimethylsilylation with bis(trimethylsilyl)trifuloroacetamide. The ten analytes appeared as separate peaks without mutual interference during 5 min. Hall's detector distinguished the ten analytes selectively from the other urinary components, which removed the need for complex clean-up procedures and led to higher sensitivity with a lower noise level. The method is sensitive enough for the assay of substances present at more than 0.1 μg/ml of urine. All the compounds could be determined with a high level of precision and accuracy, with 2–5% relative standard deviation and within ±5% deviation from the actual value. Day-to-day measurements verified the reproducibility of the method. Recovered substances were quantified by following the time course, and the analytical data together with previously obtained plasma data clarified the metabolism pharmacokinetically.

Headspace Method for Rapid Determination of Methyl Bromide in Assorted Nut Samples

Abstract A headspace method has been developed for the rapid, safe determination of methyl bromide (MeBr) in raw and processed nuts. Fifty grams of frozen nut meats is blended 3 min at high speed in 200-250 mL aqueous solution in a sealed 1 L blender cup fitted with a septum port on its cover. The cup is equilibrated 10 min in a 25C water bath. Two 250 ±150 μL aliquots of the sample headspace gas are sequentially removed with a gas-tight syringe and injected into a dual column/ dual detector gas chromatograph. One determination is made with a GS-Q wide-bore capillary column and a Hall electrolytic conductivity detector, the other with a packed column, 20% OV-101 on Chromosorb W(HP), and a 63Ni electron capture detector. The average variation for the manual injections is about 5% for both column/detector systems. To prevent random emission of MeBr during the determination, dated standards, headspace wastes, and electron capture detection effluent are passed through liquid traps. The overall recovery of MeBr from fortified samples is about 40%; the coefficient of variation is 29%. Eighteen assorted nut samples were analyzed on both systems at a quantitation limit of ᑉ100 ng/g; no detectable MeBr was found.

Gas Chromatographic Method for Determination of Chlorpyrifos and Its Metabolite 3,5,6-Trichloro-2-Pyridinol (TCP) in Dates

A method is described for the determination of the insecticide chlorpyrifos and its metabolite TCP in green, unprocessed, and processed dates with the seeds incorporated. After extraction, chloropyrifos is cleaned up using Florisil and analyzed using a gas chromatography (GC) equipped with a nitrogen/phosphorus detector. TCP is derivatized using bis-(trimethylsilyl)-acetamide (BSA) to form the TCP-derivative and analyzed by a gas chromatograph equipped with a Hall electrolytic conductivity detector. Recoveries of chlorpyrifos from all fortified dates (0.05 and 0.1 ppm) ranged from 86 to 110% with an average of 94.5%. Recoveries of TCP from all fortified dates (0.1 and 0.2 ppm) ranged from 79 to 99% with an average of 86%. Limits of detection for chlorpyrifos and TCP in green, unprocessed, and processed dates were 0.02 and 0.05 ppm, respectively.

Residue Analysis of Organochlorine Pesticides by Gas Chromatography Equipped with a Hall Electrolytic Conductivity Detector (Halogen Mode)

Residue Analysis of Organochlorine Pesticides by Gas Chromatography Equipped with a Hall Electrolytic Conductivity Detector (Halogen Mode)

Determination of the total amount sulfur in petroleum fractions by capillary gas chromatography in combination with cold trapping and a total sulfur analyzer

The distribution of sulfur compounds among fractions of a petroleum liquid has been quantitatively determined by capillary gas chromatographic techniques, including on-column injection, cold-trapping of effluent, and measurement of effective recovery. In this study the amount of sulfur was determined in the gasoline (0–450°F), light cycle oil (450–650°F), and heavy cycle oil (650–11OO°F) fractions of a refinery stream liquid. Knowledge of the amount of sulfur in the various fractions of this material can be valuable in determining how to process this material in the refinery. The petroleum liquid was separated by an on-column injection into a fused-silica capillary column, and the sulfur in each of the three cold-trapped fractions was measured by a hydrogen sulfide total sulfur analyzer. A detection limit of 50 ppm was achieved with quantitative recoveries of almost 100%. The sulfur distributions determined for a series of these petroleum liquids were 0.01–0.02 wt.-% in the 0–450°F fraction, 0.13–0.23 wt.-% in the 450–650°F fraction, and 0.50–1.20 wt.-% in the 650–1100°F fraction. The reproducibility for duplicate samples was 3%, and the reproducibility for the same sample with multiple cold-trap separations was also within 3%. This method obviates the complicated calibration step, which is necessary when sulfur-specific detectors, such as the flame-photometric detector and the Hall electrolytic conductivity detector are used.

Gas chromatographic determination of volatile sulfides at trace levels in natural freshwaters

Volatile sulfides in the aqueous phase were analyzed by degassing the solution and cryogenically trapping the volatiles. A gas chromatograph equipped with a Hall electrolytic conductivity detector is used in the sulfur mode. Water samples were analyzed with the internal standard method because of variable recoveries. Recovery efficiencies of the internal standard show a good linear relationship with the analytes. Detection limits (as S) of 0.03 ng/L for H/sub 2/S, 0.02 ng/L for COS, 0.06 ng/L for CH/sub 3/SH, 0.09 ng/L for CS/sub 2/, 0.05 ng/L for CH/sub 3/SCH/sub 3/, 0.07 ng/L for CH/sub 3/CH/sub 2/CH/sub 2/SH, and 0.10 ng/L for CH/sub 3/SSCH/sub 3/ can be achieved for a 100-mL sample. The precision is better than 10% for the range of 1-4000 ng of S/L.

Factorial optimization for flows in the hall electrolytic conductivity detector

Statistical optimization of flows is carried out for a Hall electrolytic conductivity detector (HECD). Yates' method was used to quickly estimate main factors affecting HECD response to organochlorine. Also, more detailed evaluation of variations of HECD response for three flow variables was performed via central composite design factorial experiments. Corresponding three-factor, three-level factorial experiments provided data for least-squares regression analyses. The resulting fitted-polynomial yielded an appropriate mathematical model of the HECD response surface for the corresponding three dimensions in flow-space. Optimum values for three detector flows are thereby selected from the response surface to provide maximum HECD sensitivity, i.e., response to organochlorine in the halogen mode. Supplemental data then allow for flow optimization with respect to other criteria, e.g., signal-to-noise ratios and resolution of eluates.

Residue Level Determination of the Aquatic Herbicide Fluridone and a Potential Photoproduct (N-Methylformamide) in Water

Methods are presented for the determination of the aquatic herbicide fluridone and N-methylformamide (NMF), a potential photoproduct of fluridone which has thus far been observed only in a laboratory aqueous photolysis study. Water samples are passed through a Sep-Pak C18 cartridge to extract fluridone while NMF passes unretained through the cartridge with the water. Fluridone is eluted from the cartridge with methanol, which is then concentrated for analysis by liquid chromatography with UV detection at 313 nm. The water eluate containing NMF is concentrated for analysis by rotary vacuum evaporation at 40-46 degrees C. Methanol is added to help evaporate the water, and glycerol is added as a keeper solvent to retain NMF during the evaporation. The residual NMF is dissolved in methanol for analysis by gas chromatography with a Hall electrolytic conductivity detector operated in the nitrogen mode. The assay limits of detection are 1 and 2 ppb for fluridone and NMF, respectively. Recoveries averaged 98% for fluridone at 1-400 ppb and 87% for NMF at 2-50 ppb.

Ethyl carbamate analysis in fermented products - A comparison of measurements of mass-spectrometry, thermal-energy analyzer, and hall electrolytic conductivity detector

4. References > 1000 jAg/L. Typically, the concentration is low in wine and high in some spirits; the concentration is particularly high in some plum brandies but is low in gin and vodka. Literature methods [1,2,31 rely on sample clean-up followed by packedcolumn GC and detection by FID, alkali flame ionisation, electron capture, or Coulson electrolytic conductivity detector and allow measurements down to 10 Itg/L. The clean-up procedure required for levels below 100 jg/L is extensive and MS confirmation is still required. I.5 I~a 21 In the course of a study of ethyl carbamate levels in alcoholic beverages on sale in U.K., different methods of separation and measurement were as-

Determination of Purgeable Halocarbons and Aromatics by Photoionization and Hall Electrolytic Conductivity Detectors Connected in Series

The applicability of the purge-and-trap technique, combined with a photo ionization detector (PID) and a Hall electrolytic conductivity detector (EICD) connected in series to the determination of 46 volatile organic compounds, is investigated. Both packed and open tubular capillary columns are evaluated. Twenty compounds arranged in nine groups coelute on the 1% SP-1000 on Carbopack B column, and 15 compounds arranged in five groups coelute on the n-octane/Porosil column. Preliminary experiments with wide-bore capillary columns indicate that either the VOCOL or the DB-624 open tubular capillary column can be used for the primary analysis of Methods 8010 and 8020 compounds. However, neither column is able to completely resolve all compounds. Twenty compounds arranged in eight groups coelute on the VOCOL (diphenyl dimethyl polysiloxane with crosslinking moieties, Supelco, Inc.) open tubular capillary column and 11 compounds arranged in five groups coelute on the DB-624 (cyanopropyl phenyl dimethyl polysiloxane, J&W Scientific) open tubular capillary column. Method precision of the purge-and-trap technique with a PID and a Hall EICD connected in series, as assessed from the instrument response at a known concentration per compound, is better than ± 30% (except for dichloromethane) and has a mean value of ± 12%. Method accuracy ranges from 82 to 104% for groundwater samples. Method detection limits vary with each compound and range from 0.1 to 0.9 ppb for water samples and 1 to 5 ppm for soil samples.

Determinations of polychlorinated biphenyl isomers by response factor calibration

Quantitative measurement of polychlorinated biphenyl (PCB) isomers by response factor calibration (RFC) is evaluated with fas chromatography and the Hall electrolytic conductivity detector. The procedure requires neither isomer identification nor reference compounds identical to each measured PCB isomer. Weight percent chlorine is determined for five Aroclor mixtures by RFC and compared within a few percent of expected values. Individual PCB isomers are measured and quantitatively compared for Aroclor mixtures. Also, RFC determinations for ten PCB isomers contained in a test material reference solution are compared to the supplier's stated concentrations. These RFC measurements provide quantitative analyses in the absence of a standard for each measured component.

Determination of Residual Chlorinated Solvents in Decaffeinated Coffee by Using Purge and Trap Procedure

Abstract A purge and trap method developed for the analysis of volatile halocarbons (VHCs) in table-ready foods has been applied to the determination of residual chlorinated solvents in decaffeinated coffee. Samples are stirred in water and purged with nitrogen for 0.5 h in a water bath at 100°C. The analytes are collected on a duplex trap composed of Tenax TA and XAD-4 resin, eluted with hexane, and determined by gas chromatography (GC) with a thick-film, widebore capillary column and Hall electrolytic conductivity detector. The higher levels of residual chlorinated solvents are also confirmed by full scan GC/mass spectrometry. Samples are analyzed for several chlorinated solvents including methylene chloride, chloroform, 1,2-dichloroethane, methyl chloroform, carbon tetrachloride, trichloroethylene, and tetrachloroethylene. Eleven decaffeinated instant coffees and 14 decaffeinated ground coffees representing 9 different commercial brands were analyzed by this method. Residues of methylene chloride, chloroform, methyl chloroform, and trichloroethylene were found. Highest levels occurred in ground coffees—up to 640 ppb methylene chloride. Recoveries of these 4 chlorinated solvents detected from fortified samples ranged from 96 to 106%. Brews from 3 instant and 3 ground coffee samples contained up to 1.1 ppb and 4.8 ppb methylene chloride, respectively. In addition, the resulting grounds from the brewing process were analyzed and contained up to 14 ppb methylene chloride and up to 13 ppb trichloroethylene. The limit of quantitation for these coffee grounds was 4 ppb for methylene chloride. Chromatograms from this purge and trap method are clean, enabling levels of about 10 ppb and 0.4 ppb to be achieved for chlorinated solvents in decaffeinated coffees and their brews, respectively.

Determination of polychlorinated biphenyls in waste oil by gas-liquid chromatography.

A 0.1 g portion of waste oil is cleaned up by silica gel chromatography followed by dimethylformamide-hexane partitioning and chromatography on a de-activated neutral alumina column. The purified extract is examined for PCBs by either packed-column or capillary-column gas chromatography using either electon-capture or Hall electrolytic conductivity detectors. Recoveries at the 10 mg kg–1 level are in the range 66–98% and the coefficient of variation is typically 12%. A reporting limit of 5 mg kg–1 is readily attainable and PCBs can be detected down to about 1 mg kg–1.

Identification of weathered petrol residues by high-resolution gas chromatography with dual flame ionisation detector-hall electrolytic conductivity detector

A method is presented for the detection of severely weathered petrol residues in post-fire debris. The procedure involves the splitting of the capillary gas chromatographic (GC) column effluent between a flame ionisation detector and a Hall electrolytic conductivity detector to obtain the hydrocarbon and identify petrol burned on cotton wood and weathered for 12 days. Positive identifications have been obtained by this method when applied to samples from cases of suspected arson where the GC-flame ionisation detection interpretations were inconclusive.

Application of the hall electrolytic conductivity detector to pesticide residue analysis

Application of the hall electrolytic conductivity detector to pesticide residue analysis

Analysis of some organochlorine pesticides in seafood samples by solid-phase extraction—Gas chromatography

The use of the solid-phase extraction technique for the rapid sample preparation of organochlorine pesticides is described. Samples were simultaneously extracted, cleaned, and fractionated by the solid-phase extraction method and a further separation and determination of extracted fractions was carried out by gas chromatography with either an electron capture or a Hall electrolytic conductivity detector. The percent recovery of the extracted seven pesticides was compared to that of the conventional liquid-liquid extraction method. The analytical figures of merit., chromatograms, and statistic data are reported. The application of this method was demonstrated by a real fish sample determination with mass spectra for confirmation of Kepone detection.